1. Field of the Invention
The present invention relates to a portable information terminal apparatus used as a portable telephone and the like.
2. Description of the Related Art
In the field of portable information terminal apparatus, recently, information display function has been multi-functionalized. For example, in a portable telephone, a standby screen or the like is displayed on a liquid crystal panel. Furthermore, there are portable telephones with a small camera being mounted and data picked up by the camera is stored in a built-in memory and displayed. In such structure, the amount of information for the standby screen which displays a favorite picture, etc. and the amount of image information such as the picked up data, etc. becomes extremely large compared to audio information (1,000 times larger or more). For transmitting such vast amount of information, the portable information terminal may use, as information transmitting media of the image information, optical signals which can transmit a vast amount of data at a high speed.
For example, there is proposed a portable telephone which uses optical signals for internal communication as disclosed in Japanese Patent Application (Japanese Patent Unexamined Publication No. 9-84100). FIG. 9A and FIG. 9B illustrate the structure of a conventional portable telephone. FIG. 9A is a front elevational view and FIG. 9B is a side view thereof.
In FIG. 9A and FIG. 9B, the portable telephone comprises a display operation unit 801, a platform unit 802, an RF unit 803 with an antenna 831, and a power supply unit 804. These are all separate units and each of the display operation unit 801, the RF unit 803, and the power supply unit 804 is fitted into the platform unit 802 through a fitting section a as illustrated by dash line to be connected and secured.
Further, interface units b and c, which transmits various signals between each unit, are provided between the platform unit 802 and the display operation unit 801, and between the platform unit 802 and the RF unit 803. The interface sections b and c perform communication between each block by optical couplers. For example, the interface sections b and c are formed by a combination of LED and phototransistor and are mounted to the positions opposing to each other.
FIG. 10 is a block diagram for showing the circuit structure of the conventional portable telephone. In FIG. 10, the display operation unit 801 comprises an operation input key 811, a display unit 812 such as a liquid crystal display, a control unit 913, a light transmitting unit 914 which converts a key control signal from the control unit 913 into an optical key control signal 905 and transmits it to the platform unit 802, and a light receiving unit 915 for receiving a light-state signal 906 from the platform unit 802.
The platform unit 802 comprises: a light receiving unit 923 which receives the optical key control signal 905 from the display operation unit 801 and converts it to an electric signal; a light transmitting unit 929 for sending the light-state signal 906 to the display operation unit 801; a speaker 821; a microphone 822; a light transmitting unit 924 for sending a light transmission signal 901 to the RF unit 803; a light receiving unit 925 for receiving a light receiving signal 902 from the RF unit 803; a light transmitting unit 926 for sending a light-RF-control signal 903 to the RF unit 803; a light receiving unit 927 for receiving a light-RF-state signal 904 from the RF unit 803; and a control unit 928 for controlling those units.
The RF unit 803 comprises: a hybrid 939; a radio receiving unit 932; a radio transmitting unit 933; a light receiving unit 934 for receiving the light transmission signal 901 from the platform unit 802; a light transmitting unit 935 for sending the light receiving signal 902 to the platform unit 802; a light receiving unit 936 for receiving the light-RF-control signal 903 from the platform unit 802; a light transmitting unit 937 for sending the light-RF-state signal 904 to the platform unit 802; and a control unit 938 for controlling these units. Power source 907 is supplied from a power supply unit 804 to the display operation unit 801, the platform unit 802, and the RF unit 803. The signals transmitted between the blocks are all optical signals except for the power supply.
The main object of the conventional portable telephone as shown in FIG. 9A, FIG. 9B, and FIG. 10 is to improve efficiency of manufacturing and efficiency for dealing with changes in stock and demands in terms of sales management through achieving inspections and exchanges by each unit. Each unit is connected through optical signals so that it is considered sufficient to deal with a large increase in the communication amount between the units.
However, for transmitting the same amount of signals, the optical signal communication requires a larger amount of electric power spent for converting the signals compared to the electric signal communication, since it requires photo-electrical conversion in the light transmitting units and light receiving units in each block, which causes power loss and the like. Particularly, when transmissions of signals between each block are all performed through optical signals at all times as in the case of the above-described conventional portable telephone, battery consumption is significant so that it is not suitable for long-time continuous communication.
For example, the communication information between the platform unit 802 and the display operation unit 801 is an exchange of control information for transmitting a command and status information for informing the current state. Thus, with the consideration of the extent of the communication capacity, it is not necessary to use the optical signals for the communication interface. The same is true for the control information and the status information exchanged between the platform unit 802 and the RF unit 803.